Rifle power in a submachine gun package, the HK53. It is truly neither rifle, nor submachine gun, but a strange mixture of both. A submachine gun is defined as a select fire weapon, fired from the shoulder using a pistol cartridge. However, with only an 8.3 inch barrel, the HK53 hardly qualifies as a rifle. The HK53 fills the void where pistol cartridge submachine guns like the MP5 or MP5/10 and MP5/40 may not be suitable against armored suspects.
Many parts of the HK53 are interchangeable with the MP5, they are so similar in size. The example above shows us the newer style concave buttplate that until recently was only reserved for the MP5 series. It is now available for the 33 and 53 series. The forks are slightly longer on this model than for the MP5 series. The four prong flash hider seen here is now standard. It does much more to suppress the flash from this short barreled weapon than did the more standard flash hider seen on the 33 and G3.